Given an array arr. Return True if it is an almost sorted array, and False if it's not.
arr is almost sorted if there is an element arr[i] such that the rest of the array are sorted.
i.e. arr[0] <= arr[1] <= ... <= arr[i-2] <= arr[i-1] <= arr[i+1] <= arr[i+2] <= ... <= arr[n-2] <= arr[n-1]